Cluster federation is conceptually simple. You aggregate multiple Kubernetes clusters and treat them as a single logical cluster.
Multiple clusters may be managed as a single cluster or with the assistance of federated clusters.
It is possible to create multiple clusters within the data center or cloud and then use the federation for controlling or managing them in one place.
The federated clusters are able to achieve this by doing some of the following:
Syncing resources across the different clusters: this keeps the resource sync across the different clusters in order to deploy the same deployment set across the different clusters.
Cross Cluster, discover: this provides the ability to have DNS and Load Balancer with backend from the participating clusters.